Hi welcome Rosie,
I love MFP and agree it?s a great way to watch what you eat, but I do think that 2.6lbs a week consistently is VERY VERY ambitious. More realistic would be 1.5lb on average a week.
I?ll explain why: Say your BMR is 1300, and to maintain weight with normal activity you need to eat around 1700.
To lose 2.6lb a week you need a deficit of 2.6 x 3500 = 9100 calories. That?s a 1300 deficit a day. So assuming you eat 1200 and need 1700 to remain stable, you need to burn of 500 from food a day (ie 1200 calories rather than 1700 calories) and 800 from exercise, which could be done in a hard going 90 minutes gym session ? I probably burn that on a 7.5 mile (11.5km!) run in 65 mins, but on a cross trainer would 2.5 hours! The problem is though that when I do my 750-800 cal exercise I am starving and end up eating much more than 1200 calories. I?d say I need to eat around half the exercise calories.
If you aim for 1.5lb per week then that?s a deficit of 750 a day, 500 from food and 250 from exercise ? much more realistic.
If you don?t eat enough protein and if you don?t do resistance training you?ll end up losing muscle which will make you more prone to gaining weight afterwards. Possible if you are very strict, but very hard.
I suggest ?
a) Going low fat, low carb ? ie no SUGAR, no breakfast cereal, bread, rice, pasta, cous-cous, potatoes.
b) Eat lean protein & veggies at EVERY SINGLE meal, plus some (lower sugar) fruit (apples, berries), low fat dairy and one small (100 cal) portion nuts or seeds a day.
c) Exercising each day and not eating exercise cals ? see above
d) No booze, or cheat meals etc. Go for 100 calories of treats within daily allowance say 2-3 days a week, corresponding to the exercise days.
e) Even then still not sure its possible